The invention described herein was made in the performance of work under a NASA contract, and is subject to the provisions of Public Law 96-517 (35 U.S.C. 202) in which the Contractor has elected to retain title.
Microspacecraft, also referred to as micro-,nano-, or picosatellites, depending on their size, may range in mass from under a kilogram to the tens of kilograms. Microspacecraft architectures are being considered for scientific exploration missions beyond earth orbit as well as near-earth military missions.
The use of multiple microspacecraft may increase survivability of a mission by providing redundancy and/or increase the overall capability of the system. For example, an antenna array including multiple microspacecraft, each equipped with its own antenna, may enable very high resolution observations of Earth. The reliability of the system may also be increased because the use of multiple microspacecraft provides functional redundancy, and loss of one, or even a few, microspacecraft in the array may not represent a catastrophic failure.
Making microspacecraft viable for such applications requires substantial reductions in size, weight, and power for each spacecraft subsystem. For example, micropropulsion systems capable of thrust levels in the milli-Newton range and capable of impulse bits as little as 10xe2x88x926 N*s may be required in order to perform repositioning maneuvers with the degree of precision necessary for such miniature spacecraft.
A micro-colloid thruster module is described. According to an embodiment, the module may be fabricated using silicon processing techniques, including micro electromechanical system (MEMS) techniques. The thruster module may include a number of emitters arranged in an array. Each emitter includes a propellant inlet for receiving a liquid propellant, e.g., a doped glycerol, an emitter tip, an extractor electrode, and an accelerator electrode. A voltage applied to the extractor electrode produces an electric field at the emitter tip, causing the tip to emit a beam of charged droplets.
A voltage converter converts a bus voltage to an accelerator voltage, which may be about 2 kV to 20 kV. The accelerator voltage is applied to the accelerator electrodes to accelerate the charged droplets as they exit the module.
In an embodiment, the voltage converter utilizes a transformer and a stacked array of capacitors and diodes to increase the bus voltage to the accelerator voltage. In another embodiment, an array of accelerator electrodes in an accelerator section step up the voltage to the accelerator voltage.
A controller may be provided to selectively activate emitters in the module in order to control the direction and amount of thrust. The thruster may have dimensions of on the order of about 0.1 to 1.0 cm, and provide thrust up to about 50 xcexcm and impulses of about 500 seconds to 2000 seconds.